Photolytic Degradation of Herbicide Atrazine by Radiation Ultraviolet (UVC): An Application of Green Chemistry

Abstract

Atrazine (ATZ) is an herbicide of the s-triazines classes used on crops as corn, cotton, soybean, and sugar cane. This work shows the ATZ degradation by ultraviolet radiation (UVC, 254 nm) in a bench-scale annular photoreactor. The initial concentration of the irradiated samples ranged from 2.0x10-5 to 1.2x10-4 mol∙L-1. Actinometry was used to determine the radiant energy incident on the photoreactor (1.36x10-9 einstein∙cm-2∙s-1) and the radiation source was a low-pressure mercury vapor discharge lamp with tubular glass (Phillips TUV 36 W). The conversion in 240s (27.5% - 48.7%) is related inversely with the concentration of the samples. Some results found: photochemistry reaction rate (0.9x10-9 to 2.2x10-9 mol∙cm-3∙s-1), volumetric rate of photon absorption (VRPA) (2.0x10-8 to 8.0x10-8 einstein∙cm-3∙s-1), and global initial quantum yield (0.03 to 0.05 mol∙einstein-1). For the reaction rate was proposed a phenomenological model and the process was modeled of form deterministically. The estimated values for the kinetic parameters , m, and n were, respectively: 0.03 mol∙einstein-1, 0.02 and 0.5. The kinetic model fitted the data with accuracy of 91.8%. As conclusion of the work, the photolytic degradation with UVC is an efficient process, low cost and can be used to set up pilot plants, in various scales, to reduce or eliminate compounds of the atrazine class or similar emerging contaminants, in effluents.